This invention relates to an actuator for separating electrical contacts and more particularly to such an actuator which provides rapid contact separation in a high power circuit.
It is a common requirement in high power circuits to have electrical contacts which under particular conditions must be opened or closed in extremely short periods of time. Accelerating attraction or repulsion coils are known for imparting motion to moving members carrying electrical contacts to thereby cause separation between the moving contact and a stationary contact. Devices utilizing such coils are disclosed in U.S. Pat. Nos. 3,524,957; 3,524,958; and 3,524,959 all issued Aug. 18, 1970. Multiple coil assemblies for causing separation of contacts in high power circuits are shown in U.S. Pat. No. 3,590,188 issued June 29, 1971; U.S. Pat. No. 3,551,623 issued Dec. 29, 1970; U.S. Pat. No. 3,531,608 issued Sep. 29, 1970; and U.S. Pat No. 3,549,842 issued Dec. 22, 1970.
In a high power AC circuit the advantage of opening or closing electrical contacts in time periods much less than half a cycle of the AC wave is evident when it is considered that the circuit may be thereby broken during one of the short periods of time when the instantaneous power in the circuit is relatively low. This requires precise timing of the actuation of the contacts such that opening and closing takes place at or near one of the AC wave zero crossing points. Consequently, a mass carrying one of the contacts must be moved over a distance in an extremely short period of time. If the mass is of the order of a few kilograms, the distance a few centimeters, and the time in the order of a millisecond, it may be seen that large forces must be generated to obtain the desired result. Known methods and structure for obtaining rapid contact opening and closing include imparting a destructive hammer blow to the mass carrying the moving contact. Other structure and methods include provision of repulsion coils and supplying excessive power to the coils, thereby overheating and subjecting the coils to excessive voltage stress, so that a flash over problem exists as the insulation between the coil turns is "punched through".
A repulsion coil actuator is needed which provides a high rate of contact separation without damaging the coils in the actuator, and which also provides for absorbing kinetic energy and contact latching after actuation.